[Foot tumor and diffuse pain: a case of oncogenic osteomalacia].

Oncogenic osteomalacia is a rare clinicopathologic entity, linked to a mesenchymal tumor which overexpresses a hypophosphatemic factor, supposed to be the FGF-23. To date, about 100 cases have been published. We report the case of a 40-year-old man who presented an osteomalacic syndrome with no classical etiological diagnosis. The discovery of a subcutaneous tumor of the right foot and a high serum level of FGF-23 suggested the diagnosis of oncogenic osteomalacia. Surgical removal of the tumor resulted in complete reversal of the clinical and biochemical defects. Pathologic examination revealed spindle cells associated with osteoclast-like giant cells, embedded within a myxoid matrix which showed floculent calcification. These observations were compatible with the features of PMTMCT (Phosphaturic mesenchymal tumor mixed connective tissue variant).